Computer disk drive technology has experienced tremendous advances in certain economies of scale, such as size, data compression and data density. In particular, areal density, the density of data on a hard disk drive, has increased geometrically over the last several years. In turn, the tolerances of disk drive components and their relationship to one another has also become a concern. For example, reading from, or writing to, a hard drive having a higher areal density requires close proximity between the transducer containing head and the media. With this closer proximity between head and media, comes a correlative need for the relationship between the head and media to be more regular and predictable during operation.
Complicating these concerns is that the load beams and slider may be made from any number of materials such as metals, polymers or composites all having differing and sometimes marginally compatible physical properties. The environment of use is also a concern. The load beams and slider are also the subject of high thermal stress. These components are commonly subjected to the isothermal heating generated by the various components working in the disk drive. Even more severe, the read/write head of the slider is often characterized as being the hottest part of the assembly. The read/write head is subject to the isothermal heating originating from the other disk drive components. Even further, the read/write head is subjected to joule heating induced thermal stress by the electrical work completed by the transducers in the portion of the slider.
As can be appreciated, the increase or decrease in thermal energy may have any number of effects on the materials used to fabricate the slider. These materials may expand, to different and varying degrees, when heated. In the meantime, the expansion of various elements of the read/write head may result in protrusions from the head adversely affecting fly height between the head and the media. Fly height naturally has to be of such magnitude so that elements of the head do not touch, dig, scrape, or otherwise interfere with the media.
One area of ongoing concern is the writer core on the head. The writer core is generally characterized by coils which carry current flow and, in turn, generate magnetic flux. The heat build up in this area of the head can be considerable. In the past, two general classes of materials have been used to insulate the coils. The first class of materials is commercially available, thermoset polymers. For example, U.S. Pat. No. 6,567,239 discloses liquid resist polymers used to isolate and insulate adjacent conductive lines of a coil pattern.
Thermosetting polymeric compositions are generally characterized by a high coefficient of thermal expansion and a low Young's modulus. Thus while these polymers may create irregular expanded volumes on the head, the expansion may often be mitigated. Another material used in the past is alumina which has a high dielectric character, a moderate coefficient of thermal expansion, but a high Young's modulus. Thus, while alumina does not expand to the same degree as a thermoset, the expansion, once evident, is more difficult to mitigate.
As can be seen, there is a need for further refinements in head materials and design which will allow for lower fly heights and greater areal density on media.